In virtual reality environments where a user is typically experiencing a scene as an avatar (either from the first person viewpoint or from a third person viewpoint), for example in a three dimensional display or a simulator, the image shown in the display is sometimes modified for several reasons, for example in order to divert the user's attention, to introduce objects into the display, to coordinate activities within the display and so on. The display, in particular a three dimensional display, may be used to enhance the user experience by adapting the display to the user's physical movements, such as the user's head movements. Some of these modifications and changes can be noticed by the user leading to a user experience that is not smooth.
Further, in a virtual reality application, where a user is viewing a representation of an environment through a head mounted display, it is desirable to allow a user to move around within that environment, so as to simulate an actual real world situation. However, given that a user typically uses a virtual reality system within a confined space, it is desirable to provide a way for the user to move large distances in the virtual environment relative to the actual distance moved by the user in the real world environment.
In virtual reality applications, in particular when the display is a head mounted display, such modifications typically relate to world warping and body warping. A combination of world warping and body warping may further lead to the possibility of haptic retargeting when the user is supposed to grab a real object in order provide haptic feedback. This may be used when building a structure with cubes or the like. The terms world warping, body warping and haptic retargeting are herewith explained and in particular world warping and body warping are also further explained referring to the figures.
World warping, herein is related to the function of warping the virtual world in a head mounted display for instance to motivate the user to change or follow a desired movement path in the real world. It is preferable that world warping not take place while the user is consciously viewing the virtual world or at least part of it. Thus it is preferable that it take place either while the user is not actively viewing as explained later herein or it may take place when the user is looking away by turning his head away from—and back to a scene in the virtual world whereby the head rotation is also performed in the real world. Such systems have been previously discussed in the following: “Haptic Retargeting: Dynamic Repurposing of Passive Haptics for Enhanced Virtual Reality Experiences” by Mandi Azmandian, Mark Hancock, Hrvoje Benko, Eyal Ofek and Andrew D. Wilson (ISBN 978-1-4503-3362-7/16/05). In the mentioned prior art world warping, body warping and haptic retargeting is done by motivating the user to turn his head (world warping) or while a user's limb is moving (body warping). Hybrids of world warping and body warping may be performed but usually head rotation of the user is required, since the virtual world can only be warped when the user is not seeing at least part of the scene, which is being warped.